At work we had an averaging agreement which we signed in June which said we would work 4 days a week, 10 hours a day. It said that the schedule would be repeated for 1 year, unless renewed earlier.
The Employment Standards Act http://www.bclaws.ca/Recon/document/freeside/--%20E%20--/Employment%20Standards%20Act%20%20RSBC%201996%20%2 0c.%20113/00_96113_01.xml#part4 (section 37 subsection 11) says that both parties are bound by the agreement until the expiry date or a later date, but mentions nothing (that I could find, anyway) about allowing them to change it. Section 4 mentions that the requirements and regulations can't be waived.
They ended the agreement early and gave us a new schedule for 5 days a week, 8 hours a day, effective today. They didn't have us sign anything, are they supposed to? Is this legal? Does this mean I can quit and collect EI while I go back to school or find a better job?
Also they have canceled our bonuses. I'm not sure if the bonuses were in the employment contract or not, I think they were.

Consult Lawyer.

Bonusses can be waived since they are..well...bonusses that aren't turned out on a regular basis. That is, if it isn't explained otherwise in the agreement. Read up on that.

I don't know about the whole IE thing but you'd best consult a lawyer with this. Your employer can't just turn around the whole thing at this leisure.

I would also like to add that you are most likely entitled to a Severance Pay/Package if your contract has changed and you no longer want to work for the company under the new one.

I'm not sure if it has to be in the original contract or not but if it was illegal for them to simply change the contract (Consult a Lawyer to find out) then you can tell them you don't accept the new contract and the company will essentially "Buy you out" of the remainder. It would simply be the company paying you money because you're quitting.

You guys do realize he's talking about Canadian law right?

Those Heathens have laws?